[ofa-general] New proposal for memory management

[Pavel Shamis (Pasha)]

Barrett, Brian W wrote:
> Jeff and I talked for a while today, and we're pretty sure that as long as
> the byte set by the kernel notifier is written before the pages are returned
> into the unallocated list, there isn't actually a race condition.  It does
> mean that every time the page cache is searched, we also have to check the
> byte (and likely take a cache miss), but that's not too evil.
>
> However, there's still then the problem with the notifier concept of how the
> kernel passes which pages were given back to the kernel.  It has to pass a
> (potentially very large) amount of data back to the user, so the memory
> ownership issues with kernel/user space are interesting.  It also has to
> somewhat atomically prepare the list and undset the notifier byte, which is
> also problematic.  But probably workable.
>   
It sounds like we will have another 5k lines of code in MPI that will 
try to resolve
the kernel/user notification issue :-)
IMHO, Lets avoid all these tricks and move the registration cache to kernel.

Pasha